Their skulls suggest broad faces, tiny chins and jutting brows. But to mock Neanderthals is to mock ourselves: Homo sapiens had lots of sex with Homo neanderthalensis. Neanderthal genes supply between 1 percent and 4 percent of the genome in people from homelands on several continents, from Britain to Japan to Colombia.
DNA from another human-like primate, the Denisovans, lurks in modern genomes, too. A molar and a chip of pinkie bone found in a Siberian cave provide what little information we have about this species. DNA extracted from the fragments previously revealed cross-species breeding. Yet a new study in the journal Cell shows the ancient hanky-panky did not stop in Siberia: Humans who traveled across South Asia mated with a separate group of Denisovans, as well.
"This is a breakthrough paper," said David Reich, who studies ancient DNA at Harvard University and was not involved with the study. "It's a definite third interbreeding event," one that adds to the previously known Denisovan and Neanderthal mixtures.